The invention is generally directed to medical devices and catheters designed for the treatment vascular occlusions. More particularly, the invention is directed to cardiovascular catheters having the ability to sufficiently fracture, disrupt or displace a vascular occlusion in order to allow a guidewire to pass through the occlusion within the lumen of a blood vessel. The invention is further directed to a vascular catheter for crossing a substantially occluded blood vessel by disrupting the occlusion to provide a pathway that permits the passage of a guidewire or interventional cardiovascular device such as a stent or other catheter apparatus.
Medical science has long sought effective treatments for disease states that cause stenosis (narrowing or obstruction) of the lumen (interior passage of the artery) of an artery. This condition, known generally as a vascular occlusion, is found in patients suffering from the disease of atherosclerosis (an accumulation of fibrous, fatty or calcified tissue in the arteries). Symptoms of arterial occlusion include hypertension (high blood pressure), ischemia (deficiency of circulation), angina (chest pain), myocardial infarction (heart attack), stroke, or death. An occlusion may be partial or total, may be soft and pliable or hard and calcified, and may be found at a great variety of sites in the arterial system including the aorta, coronary and peripheral arteries.
Of particular interest to cardiac medicine are the often disabling or fatal occlusions occurring in the coronary arteries (arteries supplying the heart). Traditionally, coronary artery occlusions have been treated by performing coronary bypass surgery. This is a procedure in which a segment of the patient""s saphenous vein may be taken from the patient""s leg and is grafted onto the affected artery at points proximal (upstream) and distal (downstream) to the occluded segment. While the procedure can improve the patients quality of life through reduced ischemia and angina, it is major surgical procedures with significant morbidity and mortality risks and a long convalesce period. Consequently, it is contraindicated for a significant portion of the patient population due to age and other factors. Moreover, in a significant percentage of patients, the saphenous vein graft may become occluded over the passage of time due to same disease processes which caused the original occlusion. If the patient has another saphenous vein, a second bypass procedure may be performed, once again incurring the risk, cost and prolonged hospitalization of this procedure. In fact up to 25% of bypass patients may require repeat surgery.
Newer, minimally invasive procedures are now preferred in the treatment of arterial occlusions. These procedures often include the use of long, thin, and highly flexible devices known in the art as catheters. During the procedure, the catheter is introduced into a major artery through a small arterial puncture made in the groin, upper arm, or neck, and is advanced and steered into the site of the stenosis. At the distal end of the catheter, various devices have been developed for operating upon the stenosed artery. For example, the more popular minimally invasive procedures include percutaneous transluminal coronary angioplasty (PTCA), directional coronary atherectomy (DCA), and stenting. PTCA employs a balloon to mechanically dilate the stenosis. In PTCA, a steerable guidewire is introduced and advanced under fluoroscopic observation into the narrowed artery and past the area of stenosis (e.g. blockage). Next, a balloon-tipped catheter is advanced over the guidewire until it is positioned across the stenosed segment. The balloon is then inflated, separating, fracturing or otherwise deforming the atheroma so as to enlarge the narrowed lumen of the artery sufficiently to increase blood flow to a previously ischemic or near ischemic section of the myocardium. Directional coronary atherectomy is another minimally invasive procedure that has been developed, a catheter containing a cutter housed in its distal end is advanced over the guidewire into the stenosed segment. The housing is urged against the atheroma by the inflation of a balloon, so that part of the atheroma intrudes through a window in the side of the housing. Under fluoroscopic observation, the cutter is used to shave away the atheroma. The shavings are collected in the nosecone of the housing and withdrawn along with the catheter. Similarly, stenting is another current procedure in which a wire framework, known as a stent, is compressed and delivered a balloon catheter. The stent is positioned across the stenosed segment of the artery. The balloon is inflated, dilating the stent and forcing the stent against the artery wall. The hoped-for outcome is that the stent will hold the arterial lumen open for a prolonged period. Frequently, a stent is placed in an artery immediately following PTCA or DCA. The catheters selected for many of the aforementioned procedures are known as xe2x80x9cover-the-wire catheters.xe2x80x9d These catheters depend upon the positioning of a guidewire, which typically has a flexible portion at its distal end for steering. Over-the-wire catheters cannot be positioned adjacent the stenosis to carry out current procedures until the guidewire traverses or has been advanced across the stenosed arterial segment. Thus, where the occlusion is too severe to be crossed by a guidewire or where there is not enough room for the balloon, cutter, or stent delivery catheter, neither PTCA nor DCA nor stenting can be effectively performed.
Unfortunately, vascular occlusions often contain extremely hard, calcified tissue that forms an impenetrable barrier against the simple advancement of a guidewire across the occlusion. Even a less than total occlusion may contain complex structures which may trap or divert the steering end of the guidewire. Thus, the guidewire may not completely cross the occlusion, and may become diverted into the subintimal space between the atheroma and the arterial wall, or even become buried in the atheroma. In either case, the guidewire cannot be properly positioned across the stenosis to guide a balloon or cutting element. In such cases, bypass surgery may be necessary with the associated cost, risks, and recovery period. Thus, in patients suffering from severe or total arterial occlusion, it is preferable to do what has been difficult or impossible in the past, to open the severely or totally occluded artery itself, rather than by performing a bypass. If a guidewire and working catheter can be passed through or around the atheroma, the occlusion can be treated by a number of interventional procedures include PTCA, DCA, stenting, site-specific drug and radiation delivery or a combination of these different therapies.
Accordingly, it would be medically advantageous to circumvent a vascular occlusion. Appropriate devices and procedures for crossing the occlusion should be selected without perforating the blood vessel or artery being treated, an extremely serious and even life-threatening consequence. A physician will generally not use a system which would be unsafe, nor would patients want a physician to use such a system. Therefore, solutions to the problem of crossing a vascular occlusion such as an atheroma should be safe, and in many instances, include a system of guidance for the device to bypass such an occlusion. There has been a long felt need in the practice of interventional cardiology and radiology for a reliable guidance system for these types of vascular devices. As understood by those in the art, the device often travels through a complex, tortuous vascular anatomy before it even gets to the occlusion. Then the occlusion itself often has a irregularly shaped (e.g. eccentric) morphology. Attempting to cross such an occlusion without reliable imaging of the adjacent vasculature is dangerous. For example, it is easy to dissect the tissues of the arterial wall instead of the occlusion, thereby creating a false lumen and possibly perforating the artery. If enough blood from a perforated artery accumulates in the pericardial space surrounding the heart, it will result in a condition known as cardiac tamponade in which the heart is compressed and emergency surgical intervention is required to avert heart failure and death. Physicians have attempted to avoid such adverse events through the use of imaging systems/procedures such as biplane fluoroscopy. This is an imaging system that has been used in conjunction with coronary catheterization wherein the physician observes two flat real-time x-ray images acquired from different angles. However, biplane fluoroscopy may be unreliable, costly, and relatively slow. Delay is unacceptable in many instances, for it contributes to trauma and stress and creates opportunities for complications and failures of technique. While advanced medical imaging systems may be of diagnostic interest, they are not a substitute for effective interventional treatment for severe occlusive arterial disease. There persists a long felt need in the art for a vascular device which is capable of successfully crossing an arterial occlusion with a relatively low risk of perforating the artery. What is especially needed is a therapeutic working device which assists the physician in safely restoring normal blood flow rates within diseased blood vessels. What is further needed is a vascular catheter system that may allow effective treatment of a severely occluded artery and, in particular, a totally occluded artery.
The present invention provides methods and apparatus for the treatment of vascular occlusions. It is an object of the invention to disrupt vascular occlusions or other blockages formed within blood vessels in order to provide pathways for the placement of guidewires, interventional devices and catheters as part of an overall effort to restore normal circulatory function. It is advantageous to cross a vascular occlusion by finding and/or creating a path with the least or relatively low mechanical resistance through or around the occlusion. The invention further provides apparatus and methods to tear or to mechanically fracture a vascular occlusion, or to separate a vascular occlusion from a blood vessel wall, with minimal risk of perforating the adventitia of an arterial wall.
One aspect of the invention provides apparatus for treating a vascular occlusion. A catheter may be selected comprising an elongated shaft that is formed with at least one lumen extending from the proximal section to the distal section of the shaft. A hinged spreading member may be positioned at the relatively distal section of the shaft. The spreading member may include a distal most end that moves in a substantially lateral direction away from the central axis of the shaft to disrupt a vascular occlusion. An actuating assembly may be also positioned along at least a portion of the elongated shaft to move or to direct the distal most end of the spreading member in response to an applied actuation force. The actuating assembly may further include a cam follower or other guiding region that is formed on a relatively interior portion of the hinged spreading member.
Another embodiment of the invention includes an intravascular catheter for expanding or stretching vascular tissue. The intravascular tissue expanding catheter may include a catheter shaft defined by a distal end having at least one conduit extending along the longitudinal axis of the catheter shaft. A housing may be formed at the distal end of the catheter shaft wherein the housing includes at least one hinged deflecting member defined by a distal most tip that moves in a substantially lateral direction away from the central axis of the shaft to expand tissue surrounding a vascular occlusion. An actuation assembly may be also positioned along the catheter shaft to move the distal most tip of the hinged deflecting member away from the central axis of the shaft. The catheter shaft may be also formed of braided material and a flexible inner coil shaft component that supports a column load.
It is a further object of the invention to provide a vascular catheter that is formed with a tissue expansion assembly for tearing or fracturing an occlusion within a blood vessel. The vascular catheter may comprise a catheter body formed with a distal section and at least one longitudinal conduit. At least one tissue expanding member may be connected to the distal section of the catheter body. The expanding member may include a relatively proximal portion and a relatively distal portion wherein the distal portion is configured to spread apart relative to the proximal portion of the expanding member. An actuation assembly may be positioned within the catheter body, and may be in communication with the proximal portion of the tissue expanding member to spread apart the distal portion of the expanding member. The distal section of the catheter may further include a relatively fixed extension. The relatively proximal portion of the tissue expanding member may be connected to the fixed extension with a hinge pin to permit the relatively distal portion of the tissue spreading member to move away from the fixed extension.
It is an additional object of this invention to provide flexible catheter shafts that support variable column loads. The shaft may comprise an outer catheter shaft defined by a longitudinal shaft lumen. An inner coiled body that is defined by a longitudinal coiled lumen may be positioned within the longitudinal shaft lumen for column load reinforcement of the outer shaft. A movable pulling element may be slidably positioned within the longitudinal coiled lumen for relative movement of the pulling element with respect to the inner coiled body. Another variation of the invention is to provide a catheter shaft with a reinforced outer catheter shaft. An outer shaft may be formed with a lumen that includes an inner shaft positioned within the outer shaft lumen. The inner shaft may further include an actuation lumen and at least one inner shaft lumen, and may be formed by extrusion. A column load reinforcement sleeve may be formed with a sleeve lumen that is positioned within the actuation lumen. In addition, an actuation wire may be slidably positioned within the sleeve lumen to provide relative movement of the wire within the sleeve. At least one inner shaft lumen may be also configured for placement of a guidewire. In yet another variation, a reinforced catheter body may be selected having a braid reinforced catheter shaft formed with a longitudinal catheter shaft lumen. An actuation conduit and a guidewire conduit may be separately formed within the longitudinal lumen of the catheter shaft. Additionally, a compression or wound coil that provides compression support may include a coil lumen and may be positioned within the actuation conduit for column load reinforcement of the actuation conduit. A pulling element may be positioned within the coil lumen for relatively slidable movement within the coil.
Another object of the invention is to provide an intravascular catheter for expanding tissue that includes a catheter body formed with an outer reinforced shaft coaxially formed about an inner coiled body for column load reinforcement of the catheter body. The inner coiled body may further include an actuation conduit leading to a relatively distal section of the catheter body. A tissue expanding member may be connected to the distal section of the catheter body. The interior surface of the tissue expanding member may include a cam follower. Additionally, the expanding member may be defined by a relatively proximal portion and a relatively distal portion so that the distal portion is configured to expand relative to the proximal portion of the expanding member. An actuation element may be selected and positioned within the actuation conduit formed in the inner coiled body. The actuation element may be formed as a wire or tube that supports actuation forces, and may further include a cam for communication with the interior cam follower of the tissue expanding member to expand the distal portion of the expanding member when actuated. The surface of the cam includes a variety of curved or non-linear configurations, and is preferably complementary to the shape of the corresponding cam follower.
Another aspect of the invention includes methods for disrupting and crossing a vascular occlusion. The vascular occlusion may be separated, fractured or displaced to provide a pathway across the obstruction in order to accommodate the placement of a guidewire or interventional device as part of an overall effort to restore normal circulatory function within the blood vessel.
It is an object of the invention to provide methods of displacing a vascular occlusion by initially selecting a vascular catheter that is formed with a spreading member positioned at the distal region of the catheter. The spreading member may be configured to spread or stretch apart an occlusion and/or vascular tissue, and may be activated or actuated in response to a directed force along the longitudinal axis of the catheter. An actuator assembly may be positioned along at least a portion of the catheter to transmit the directed force which may be applied linearly or rotationally, or by transmitting pressure relatively distally to an actuation balloon, from a remote or proximal portion of the catheter to the spreading member. The vascular catheter may be positioned adjacent to a substantial or total vascular occlusion within a selected blood vessel before applying a directed force to the actuator in order to deploy or to spread apart the spreading member. The occlusion may be displaced or disrupted based upon the different elastic properties between stretchable blood vessel walls and materials which form vascular occlusions. The vascular occlusion itself may be also fractured or otherwise disrupted to provide a passageway across the occlusion in order to accommodate the placement of a guidewire or interventional device such as a stent after removing the vascular catheter from the selected blood vessel. The spreading member may be spread apart to disrupt a vascular occlusion to create a path substantially through or around at least a portion of the occlusion. Additionally, the spreading member may stretch out the blood vessel wall creating a path substantially between the occlusion and the blood vessel wall. When the vascular occlusion is adhered to the wall of a selected blood vessel, the spreading member may be also expanded or spread apart to separate the layers of the blood vessel wall. The vascular catheter may be distally advanced through the vascular occlusion to pass through at least a portion of or entirely through the occlusion. Another variation of the invention includes the method of selecting a guidewire and passing the guidewire through a conduit formed in the vascular catheter. The guidewire may extend along to the length of the catheter and reach the site of an occlusion. Upon activation of at least one spreading member, the guidewire may be advanced through or around at least a portion of the occlusion.
Other various methods of crossing a substantially occluded blood vessel are provided herein in accordance with the concepts of the invention. An intravascular catheter may be selected that includes a distally mounted tissue expanding member defined by a relatively proximal portion and a relatively distal portion so that the distal portion is configured to expand relative to the proximal portion of the expanding member. In addition, an actuation assembly may be positioned within the intravascular catheter to transmit a spreading force in order to expand the distal portion of the expanding member. The tissue expanding member may be placed or positioned within a blood vessel in proximity to an occlusion, and subsequently activated to stretch the blood vessel wall and disrupt the occlusion to permit the passage therethrough. The tissue expanding member may be deactivated thereafter, and the intravascular catheter removed from the target blood vessel. A guidewire may be positioned within the passageway formed within or alongside the disrupted or displaced occlusion in order to facilitate the placement of a stent or other interventional device. The guidewire may also pass through at least a portion of the occlusion before the tissue expanding member is deactivated. The catheter may be similarly advanced through or across at least a portion of the occlusion upon disruption of the vascular obstruction.
In yet another variation of the invention, a method is provided for crossing a coronary vascular occlusion. This procedure may begin by selecting and advancing a guidewire within a blood vessel to a vascular occlusion. An intra-coronary guiding catheter may be advanced over the guidewire so that the distal end of the catheter is in proximity to the vascular occlusion. The guidewire may be thereafter removed from the blood vessel. An intravascular catheter may be selected for placement within the guiding catheter that includes a spreading member positioned that is responsive to directed force along its longitudinal axis. Additionally, an actuator assembly may be positioned along the intravascular catheter to transmit a directed force applied from the proximal portion of the catheter to the spreading member. The intravascular catheter may be advanced through the intra-coronary guiding catheter to position the spreading member of the intravascular catheter substantially adjacent to the vascular occlusion within the blood vessel. A directed force may be applied to the actuator assembly to spread apart the spreading member in order to displace the vascular occlusion. Another variation of this method may include the advancement of the intra-coronary guiding catheter past or across the occlusion before removing the intravascular catheter from the blood vessel. In addition, a guidewire may be advanced past or across the displaced vascular occlusion after removing the intravascular catheter and before removing the intra-coronary guiding catheter.
Other variations of the invention described herein include a vascular catheter formed with a blunt end assembly for tearing or fracturing an occlusion within a blood vessel. It is an additional object of this invention to provide such an assembly wherein the assembly includes a catheter having a distal end and a proximal end and wherein a working end member fits in an interchangeable manner to the distal end of the catheter and wherein the working end comprises a blunt end member in accordance with the invention. It is an additional object of this invention to provide such an assembly wherein the blunt end member has a first closed position and a second open position and may be repeatedly opened and closed for tearing/fracturing the occlusion within the lumen of the blood vessel. It is a further advantage of the invention to provide a tearing or fracturing force that is stably applicable to a severe or total arterial occlusion. A mechanical working element may be stably operable upon a severe or total arterial occlusion in a manner unlikely to perforate the adventitia or other layers of the arterial wall. In addition, the blunt end member assembly may comprise: a blunt end member connectable to the distal end of the catheter, the blunt end member sized and shaped for fitting within the blood vessel and for tearing and/or fracturing the occlusion, the blunt end member having a first position for allowing the blunt end member to be located at the occlusion and a second position for fracturing the occlusion; and an actuation member for moving the blunt end member between the first and second positions, whereby the blunt end member is connectable to the distal end of the catheter and the blunt end member is deliverable to the occlusion in the first position and is actuable to a second position for fracturing the occlusion.
In one embodiment of the invention, an over-the-wire vascular catheter is provided comprising a blunt end member disposed at the distal end thereof and a securing balloon disposed about the distal end zone of the catheter proximal to the blunt end member. The catheter and blunt end member may be sized and shaped so as to allow the blunt end member to be advanced into contact with an occlusion in an artery. The balloon may be disposed on the outer surface of the distal end zone of the catheter and is inflatable to secure the distal end of the catheter within the artery, and thus to maintain engagement or longitudinal registration of the blunt end member with the occlusion. A balloon inflation lumen may be provided in the catheter. The blunt end member may comprise four jaw sections flexibly attached to the distal end of the catheter, and may be arranged symmetrically about the longitudinal axis thereof The catheter may comprise a retractable actuation shaft having a ball-shaped ferrule fixed to the distal end thereof between the jaw sections. To accommodate a guidewire, the actuation shaft may include a lumen and the ferrule includes a center opening. The jaw sections may have a first, closed position in which the catheter may be advanced to engage the jaws with the occlusion. When the actuation shaft is retracted, the ferrule or cam impinges upon the inner surfaces or cam followers of the jaw sections, urging them apart toward a second, open position to fracture the occlusion. The ferrule may be formed with a fiusto-conical profile.
In another embodiment of the invention, each jaw section may include a rectangular distal end or a spade-shaped configuration. In the first, closed position, the jaw sections form a channel substantially confining the guidewire to the longitudinal axis of the blunt end member. It is an advantage of this embodiment that when the jaw sections are in the first, closed position, a guidewire may be advanced into a portion of the occlusion bounded by the points of contact with the distal ends of the jaw sections. In another embodiment of the invention, the jaw sections may be fabricated from an alloy comprising nickel and titanium. It is an advantage of this exemplary embodiment of the invention that the superelastic properties of the alloy facilitate closing of the jaw sections when the ferrule is deactivated or de-actuated by an actuation member.
In another exemplary embodiment of the invention, the actuation member includes an actuation cable disposed in the catheter. The proximal end of the cable is manipulable from the proximal end of the catheter and the distal end of the cable is attached to the ferrule. It is an advantage of this exemplary embodiment of the invention that the cable increases the tension capacity of the actuation member during retraction of the ferrule. A part of the lumen of the actuating member may include a friction reducing coating. It is an advantage of this embodiment of the invention that the catheter slide easily over the guidewire. In another embodiment of the invention, the mating surface defined by the impingement of the actuation member upon the blunt end member includes a friction reducing coating. It is an advantage of this exemplary embodiment of the invention that the actuation member encounters minimal frictional resistance while urging the jaw sections apart.
In another embodiment of the invention, the entire blunt end member may be fabricated from a single piece of material. It is an advantage of this exemplary embodiment of the invention that fabrication of the blunt end member does not require attachment or assembly of multiple parts.
Another embodiment of the invention provides a blunt end member that includes a rigid tubular reinforcing member slidably disposed about the actuation shaft inside the distal end zone of the catheter. A tubular support member is disposed on the outer surface of the distal end of the catheter. The distal end of the support member includes a spring member deformably supporting a plurality of jaw sections. The support member may be crimped onto the distal end zone of the catheter, securing the catheter onto the reinforcing member. It is an advantage of this embodiment of the invention that a simple yet secure attachment is formed between the catheter and the blunt end member.